This is a competitive renewal application for a project addressing the neurological mechanisms of spatial attention. The proposed studies will use the methodology of functional magnetic resonance imaging (fMRI) and will be conducted on young volunteer subjects. Spatial attention is frequently impaired in patients with brain damage. The most common impairment of spatial attention is known as hemispatial neglect. This condition interferes with the ability to attend to the environment and severely disrupts a wide range of daily living activities ranging from reading to driving. Up to 82% of all patients with damage in the right side of the brain display some manifestation of this syndrome. More than 20 years ago, work on brain damaged patients led us to propose that spatial attention was normally controlled by a large-scale network of interconnected areas in the cingulate gyrus, frontal cortex, and posterior parietal cortex. During the past project period, we used fMRI methodology to establish the face validity and general outlines of this network. These experiments raised new questions and hypotheses related to the internal organization of the attentional network. Our goal during the next project period is to pursue these questions and hypotheses with the help of functional magnetic resonance imaging (fMRI). We have three broad goals, each containing multiple questions raised by experiments performed in the current project period. Our first goal is to delineate functional segregations within the parietal, frontal, and cingulate components of the attentional network. Our second goal is to determine the way in which the attentional network interacts with other networks related to motivation, eye movements, and working memory. Our third goal is to address the nature of hemispheric asymmetry in spatial attention. We designed 7 experiments and generated specific hypotheses in order to pursue these goals. The proposed experiments will address new questions on visual search and the relationship of spatial attention to reward and punishment. The results of these experiments will help to understand the neurological bases of spatial attention and may lead to more rational treatments of hemispatial neglect.